An air compressor is a device that increases pressure by compressing air in a sealed container using a power source. An electric motor, a steam engine, and an internal combustion engine, etc. are used for the power source. Such power sources include a reciprocating type that reciprocates a piston, a rotary type that rotates a rotor, and a centrifugal rotary type that uses centrifugal force by blades that are rotated at high speed.
Compressed air is air with the volume decreased and the pressure increased by pressurization thereof. In everyday life, various types of work are performed using the force when high-pressure air decreases in pressure. For example, the force is used for ventilation of subways, mine drifts, and buildings.
The air pressure that is used in these cases is about 0.1 kg/cm2 for ventilation of subways, drift mines, and buildings; about 0.5˜1 kg/cm2 for burning cokes in a furnace at a steelwork or a foundry; about 0.5˜1 kg/cm2 for delivering powder such as cement or pulverized coal or grains into a sealed pipe; about 7 kg/cm2 for a pneumatic hammer, a pneumatic drill, and a rivet hammer, etc.; about 7 kg/cm2 for the brake or a door engine of a train; and about 50 kg/cm2 for spraying fuel in a diesel engine. Further, in other special cases, compressed air of 100˜150 kg/cm2 is used for sinking and floating of a submarine.
There is no possibility of ignition in a motor using compressed air, so it is used in a coal mine or a chemical factory where there is danger of explosion. The types of motors are classified into a steam engine type, a rotary radial crank type, a rotary radial cylinder type, a gear type, and a rotary blade type, etc.
A leak sensor, which is a sensor that senses water, senses whether water leaks or not.
The leak sensor generates a sensing signal by sensing the difference in frequency when there is water and there is no water on a floor in normal times.
A servomotor, which is an operating unit in a servo mechanism, is a device that controls loads in response to control signals. A servomotor is classified into an electric type (servo electric motor), a pneumatic type (pneumatic servomotor), and a hydraulic type (hydraulic motor) in accordance with the power source, and a servomotor usually means a servo electric motor.
A servo electric motor, which is an electric motor for control and which has high-speed response and a large speed control range, is classified into a DC servomotor and an AC servomotor in accordance with the power. Most AC servomotors are 3-phase servomotors.
These repeat stopping, starting, and backward operating, so they are designed to have high heat dissipation efficiency or to quickly change the operation. Servomotors are operated in response to control signals, and for this purpose, they require a device that receives and amplifies control signals, and the device is called a servo amplifier.
A manometer is a device for measuring the pressure of gas or liquid and there are various types of manometers, depending on the use, such as a barometer, a pressure difference meter, a high pressure gauge, and a vacuum gauge.
Depending on the measuring principle, for example, there is a manometer that measures pressure using balance with the weight of a substance such as liquid, an elastic manometer that measures pressure using the degree of bending of a pressed elastic body, and a gauge that uses predetermined physical properties that are changed by pressure.
A U-tube manometer formed by filling a glass tube with water, mercury, or alcohol is representative of the manometer. When an end of the tube is connected to an object to be measured, the liquid moves up or down to the position where it equilibrates with a pressure change between both ends of the tube. In this state, it is possible to measure the pressure difference between both ends on the basis of the height difference of the liquid at the left and right sides of the tube. There are an open type and a closed type, both of which have wide measurable ranges.
A mercury barometer is not a U-shaped pipe, but is a closed type barometer that is the same in terms of the principle of operation. A type of mechanically enlarging movement of a float on liquid or converting the movement into an electric amount is used in the engineering field.
Further, the elastic pressure gauge is relatively widely used for the industry and measures pressure by mechanically enlarging transformation of a pressure-receiving member made of metal, etc. There are a bourdon tube pressure gauge, a diaphragm pressure gauge, and a bellows pressure gauge (including an aneroid manometer), etc. These pressure gauges are simple to handle and have a wide measurement range, but they have a common deficit that the elasticity of the pressure-receiving member has little hysteresis and has non-uniform transformation to pressure, and that the transformation is increased when pressure is applied for a long period of time.
Further, the vacuum gauge is a device for measuring pressure under atmospheric pressure, and other than the manometer or the elastic pressure gauge, there are special pressure gauges such as a Macleod gauge, a pirani gauge, and an ionization gauge that measure changes in thermal conductivity or ionization degree of gas due to changes in pressure.
A deadweight gauge is a kind of high-pressure pressure gauge that measures pressure using a weight. The deadweight gauge measures pressure by making equilibrium between the pressure, which is generated by oil such as coal oil taken into a cylinder with a piston therein and pushes up the bottom of the piston, and the sum of the weight of the piston and a weight on the piston. Such a deadweight gauge can measure high pressure that the manometer cannot measure, and is used for correcting the scale of other pressure gauges.
Further, as high-pressure gauges that measure high pressure of fluid, there are a compression pressure gauge, a resistance pressure gauge, and a bourdon tube pressure gauge, etc.